Brad Plumer, a writer I sincerely hope you follow on Twitter, has a new piece up about the infamous 2C “safe” limit of global warming. This is an absolute must read piece, and I hope everyone reading this site who hasn’t read it already does so.

Brad’s article is: Two degrees: How the world failed on climate change. While I won’t comment on it in detail, partially out of a desire to push you to go read it and partially because I don’t have a lot to add, I do want to chime in on three points about the overall concept of a 2C “safe” limit:

First, the basic idea that 2C of warming over pre-industrial times (or any other specific limit measured in global average temperature) is a sufficient way to specify a guideline is naive. Just as important is the rate of change, as quick change will ripple through the environment and cause much more ecological disruption than would slow change resulting in the same absolute temperature level. We could certainly define a “safe” limit so low that accelerating from pre-industrial temps to the limit would cap the rate of change, but we’ve likely already blown by that ultra-conservative limit at our current 0.8C.

Second, even ignoring the rate-of-change argument, claiming that 2C is “safe” is making an exceedingly broad and shaky claim. As I pointed out in a post on this site in late 2010 (Some perspective on 2C for the new year), there was a kind of “proto-IPCC” UN effort involving 152 committee members from 58 countries that published their findings in the book Only One Earth in 1972 that said (page 192; emphasis added):

Clearly man has had nothing to do with these vast climatic changes [moving in and out of ice ages] in the past. And from the scale of the energy systems involved, it would seem rational to suppose that he is not likely to affect them in the future. But here we encounter another fact about our planetary life: the fragility of the balances through which the natural world that we know survives. In the field of climate, the sun’s radiations, the earth’s emissions, the universal influence of the oceans, and the impact of the ice are unquestionably vast and beyond any direct influence on the part of man. But the balance between incoming and outgoing radiation, the interplay of forces which preserves the average global level of temperature appear to be so even, so precise, that only the slightest shift in the energy balance could disrupt the whole system. It takes only the smallest movement at its fulcrum to swing a seesaw out of the horizontal. It may require only a very small percentage of change in the planet’s balance of energy to modify average temperatures by 2°C. Downward, this is another ice age; upward, a return to an ice-free age. In either case, the effects are global and catastrophic.

Since 1972 we’ve learned a lot about how the systems and subsystems, the fundamental architecture, of our planet’s biosphere interact, thanks to the tireless and often unrecognized efforts of many, many researchers and scientists. And those revelations are overwhelmingly bad news, from the outbreak of pine bark beetles to quicker than expected loss of polar ice to desertification and much more. I’ve been reviewing a lot of my file archives recently, and I’m constantly running across phrases like “worse than expected” in articles reporting scientific findings. So if we figured out in 1972 — when the original Apollo moon missions were still underway — that 2C of warming was a very bad idea, what can/should we conclude about it in 2014?

Third, Brad’s article is one of the very few I’ve seen to date that said plainly and directly that there’s almost no chance we’ll remain below 2C. This is the next great cognitive boundary we’re about to breach, the widespread recognition that we’ve blown it on 2C and now have to work even harder to avoid much worse impacts from 4C or even 6C by 2100. This change in public dialog is certainly not something anyone should be happy about, except in the very narrow sense that it’s a step toward doing something about an immense problem.

I concluded a while ago that 2C was a pipe dream based on a very simple analysis: If you add up the warming that’s already happened, the warming we can expect from the already emitted CO2 that hasn’t happened yet (thanks to that whole “love is fleeting but CO2 is forever” thing I constantly harp about), and add in the warming from our emissions released during even a very aggressive decarbonization effort, we’re right on the brink of passing a commitment to over 2C of warming.

And lest anyone forget, we’re still building new and non-CCS-capable coal plants at a horrific rate. The IEA recently tweeted the fact that (from 2005 to 2012 China added 150MW of new coal-fired capacity every day). I’ll leave it as exercise for the reader to figure out the cumulative CO2 emissions from all that new capacity if it runs for the expected 40 to 60 years. And that’s not even talking about American SUVs, Indian coal, and all the other ways humanity finds to turn fossil fuels in the ground into warming CO2 in our air and acidifying CO2 in the ocean. Any belief that we’ll suddenly have an attack of enlightened self-interest and quickly decarbonize our worldwide economy assumes “facts not in evidence”, as lawyers say.

This is why I’ve been saying for a long time (in blogosphere years) that there’s basically zero doubt we’ll have to resort to one or more geoengineering technologies in the coming decades. The impacts will mount and become quite painful and expensive, including not just adaptation (e.g. building sea walls) but also disaster relief, such as rebuilding after coastal storms or aiding potentially tens of millions of climate refugees. The latest IPCC report, specifically the Working Group III portion, openly talks about large scale efforts to remove carbon from the air and permanently sequester it. I think it’s clear that once we adjust to talking about being beyond 2C of warming, the next cognitive hurdle will be talking about the inevitability of geoengineering. That’s when things will get not just more interesting than most of us imagine, but more interesting than we can imagine.

It's a shame that the big companies would consider the expense and effort involved rather than to develop and deploy the least expensive solution to actually cutting excess CO2. Presently, that is nuclear, but nuclear has its billions of haters.

I believe that 650,000 sq km of solar panel would do the job if cheap. Instead of a dollar a watt, the price must come down to just $20/sq m, made in giant machine automated factories developed by the international necessity to save the biosphere. At $20/sq m for installation and another $20/sq m equivalent for storage, that's about 60 trillion dollars. Is it really that impossible for 1.5 billion people to afford the $3 a day to do this (assuming 25 year system longevity)? From there, 10 billion people on a (by then) completely modernized (and economically developed) planet should easily afford the continual replacements and updating of such an awesome solid state global grid.

Less than 1% of the Earth's land covered by solar includes the electrification of transport, as well for up to 10 billion people (assuming other efficiency improvements). From a traditional cost of energy point of view, we all could easily afford this (thus allowing room for required profits to get the ball rolling) once billions more people modernize theemselves via global economic activity.

If we can't convince the world to do this (or nuclear) then the future is toast.

Ken Caldeira is a leading researcher studying geoengineering. Eg: he coined the term SRM, i.e. "solar radiation management".

Some years ago he attended a talk given by an advocate of what has become known as SRM and he stood up and denounced the guy giving the talk, saying this is impossible. He then went back to his lab and ran some simluations and discovered that it probably is possible to return Earth's temperature to the preindustrial even with the extra CO2 civilization is liable to put in over the next decades fairly cheaply.

He's done a lot of research in to the topic by now. He doesn't advocate SRM, except as an emergency treatment similar to giving morphine to a cancer patient. His idea of when civilization should start employing SRM is after it has stopped building new things that use the atmosphere for a waste dump.

He's put a certain amount of effort into coming up with an explanation of what he knows suitable for the general public. An example of how he explained things a few days ago in an interview is available here

Thanks David, in that interview Caldeira clearly sees geoengineering as only a palliative measure, and emphasizes that transformation of our energy systems is the only way we can move to effectively solve the problem.

Aerosols in the stratosphere are certainly not perfect or sufficient by themselves, but would need to be part of a grand strategy- albedo control, carbon sequestration from the air and the sea, plus of course a switch to low carbon energy and better land use. But the effects of Pinatubo showed that the initial cooling was followed by negative feedbacks- less water vapour in the air, less outgassing of CO2 from the oceans, more reflective snow.

Another feedback we could turn to our advantage is ocean fertilization. During the ice ages, windblown dust from the wide expanses of barren glaciated soil was carried out over the oceans, stimulating algal growth in normally barren areas, and so pulling more CO2 out of the air and intensifying the cooling effect. Iron and other minor nutrients spread into the southern ocean should have the same effect. Grinding up ultramafic rock, perhaps using off-peak nuclear power, would also simulate natural weathering on steroids, without the need to separate the dissolved CO2 and pump it to the sea floor. Your membrane alkalinity/acid scheme is the same as the US Navy proposal for making carbon neutral synfuels; while that would only temporarily lower ocean acidity, till the fuel was burnt, it would be a lot better than continually extracting new hydrocarbons for uses where clean electricity was impractical.

I ran some calculations for quantitative perspective. Calculated the power needed to sequester the CO2 from 10 gigatonnes of carbon per year (37 Gt CO2) at 0.7 electron vols per molecule. 10 Gt carbon is 227 trillion moles, or 1.7 E38 molecules. Energy needed is 21.9 E18 joules per year, which works out to 694 gigawatts. Bump it up to 800 GW (0.8 TW) to cover inefficiencies and pumping losses, and it's 33% of the world's ~2.4 TW average of electricity production. A lot of power, but not impossible.

The method I assumed for calculation purposes is one that hasn't received much attention. In my opinion, however, it's the most practical. It's less energy-efficient than the "usual suspects", but should be more capital efficient. It uses ocean capture via enhanced alkalinity in surface waters.

The process disproportionates sea water into a large slightly alkaline fraction and a small highly acidic fraction. It uses bipolar membrane electrodialysis. The alkaline fraction is sprayed onto the ocean surface over a broad area; the acid fraction is injected into porous volcanic basalt deposits on the sea floor. The acid is neutralized there by reaction with silicate rocks. The reaction produces SiO2 and metal cloride salts.

The end result of these reactions is exactly the same as removal of atmospheric CO2 by natural weathering of rocks. It's just millions of times faster. It's an air capture technology that employs the entire ocean for a "capture surface", It thus captures emissions from vehicles as well as power plants and requires no equipment at individual power plants. Also no pipelines transporting compressed CO2 to geological sequestration sites.

All it needs is a few trillion $ to sprinkle a few million plants around the world's oceans and supply the collective 800 GW of zero-carbon power they need to operate. Piece of cake, no?

Engineer- Poet, there's not a lot of scientific backing suggesting we'd buy any time at all:

Aerosol geoengineering hinges on counterbalancing the forcing effects of greenhouse gas emissions (which decay over centuries) with the forcing effects of aerosol emissions (which decay within years). Aerosol geoengineering can hence lead to abrupt climate change if the aerosol forcing is not sustained. The possibility of an intermittent aerosol geoengineering forcing as well as negative impacts of the aerosol forcing itself may cause economic damages that far exceed the benefits.

Meanwhile, big business not only sees geoengineering as a license but an imperative to head off carbon taxes. Oil-industry-backed conservative stalwarts like the American Enterprise Institute, the Cato Institute, and the Heartland Institute overwhelmingly back unproven geoengineering strategies either as a substitute for emissions reductions or a delaying tactic:

The Cato Institute (denialists), whose senior fellow and director of natural resource studies, Jerry Taylor, says that if we end up forced do something about global warming, “geo-engineering is more cost-effective than emissions controls altogether.”

The Heartland Institute (denialists), whose David Schnare now advocates geoengineering as quicker and less costly to the economy than greenhouse gas reductions:

“In addition to being much less expensive than seeking to stem temperature rise solely through the reduction of greenhouse gas emissions, geo-engineering has the benefit of delivering measurable results in a matter of weeks rather than the decades or centuries required for greenhouse gas reductions to take full effect.”

Who cares what the denialists want? What matters is getting necessary things done. If we need geoengineering to keep some sort of climactic sanity in the arctic regions while other measures catch up, we should do it. Worse for the climate is not better for politics; we can't allow things to get to tipping points, and having geoengineering methods to e.g. yank tundra temperatures down if methane releases start rising rapidly is just good sense.

Getting denialists to agree to some measures means they cede ground. Again, cutting summer heat gains near the poles won't do anything to stabilize wind patterns during winter, when the region is in permanent darkness. We'll still have things like wandering polar vortices to remind the public that things are very much NOT normal, and if the aerosols have fallen out by November they can't be blamed.

Denialists will lose credibility all by themselves. We've got to get on with work.

Geoengineering is being portrayed as an alternative to fossil consumption, not a remediation aid. There are billions at stake for fossil fuel industries, and the messaging will be (and is being) crafted to present it as such. Do you really believe that an onslaught of lobbying and PR will be unable to explain away concepts as abstruse as "wandering polar vortices" to a largely-ignorant public, when that same PR machine has successfully sown doubt about global warming for three decades?

You characterize geoengineering as a "necessary thing" and "just good sense" without any proof that it would be effective, or refuting studies which clearly show it could make things much, much worse. It will do nothing whatsoever to address the crisis of ocean acidification. And we have no control group on which to compare trials so full-scale research is impossible - which means putting hundreds of millions of lives at risk before we even know it will work.

The whole idea is unacceptably reckless, a responsibility dodge, and a deflection of resources from where they could do far more good.

The analysis looked at volcanic events, including the Pinatubo eruption (I could not find the paper and could not determine if it included the recent event in Iceland). It apparently did not occur to anyone that location matters. Pinatubo is practically on the equator; its stratospheric haze circled the globe and worked its way north. If the stratospheric injection was done at latitudes higher than 50° north, especially where the stratospheric circulation is descending and particles are falling out, the likelihood of affecting Africa is much reduced.

If we can delay the onset of arctic ice melting and reduce the amount of loss, we might be able to delay that particular tipping point. Note, I said delay. You're absolutely right that it will have no effect on acidification, and will probably have side effects that we cannot predict. That does not make it a bad thing to do; it may well be the least evil of our options.

We don't know if they do or not, or if they'll even exacerbate the problem, or create horrific new ones. Most importantly, it's becoming a license to continue business-as-usual without making the difficult and expensive choices we really need to make.

The answer is not complicated: leave fossil fuels in the ground. It's amazing to me the logical gymnastics we perform in order to avoid that inescapable fact.

We do know that natural phenomena have substantial effects on Earth's radiative balance. Volcanic eruptions in particular can cause substantial cooling effects. The same materials (SO2), applied where and when desired (polar stratospheric regions, during the daylit seasons) can help cool the poles. We may also be able to create more localized effects.

I'm not sure anyone would take this as a license to continue as before. If we could un-do the summer warming at the poles, we'd still be unable to fix the winter radiative changes which caused our wandering polar vortex. All this would do is buy time. Maybe, just maybe, we can buy enough.

I really, really don't like the pumping-aerosols-into-the-stratosphere approach. It's cheap and easy, I'll grant it that. But in addition to unknown impacts on weather patterns and rainfall, it does nothing to counter ocean acidification. We're already not that far away from a mass extinction of shellfish, corals, and calcareous phytoplankton. Such a drastic change in ocean ecosystems would be a Very Big Deal.

Well, yes, as an emergency measure. Hard to argue with that. Modest cost and the speed with which it could be deployed do make aerosol-based SRM a likely candidate for emergency action.

The trouble is that once an emergency action has knocked the "edge" off a problem, the temporary solution too easily slips into becoming the permanent solution.

There's some irony here, in that how I feel about aerosol-based SRM is similar to how many environmentalists feel about CCS in general. They fear it will provide cover for continuing to burn fossil fuels for as long as they remain cheaper than the alternatives. They're right, of course.

The difference, in my opinion, is that their opposition to fossil fuels is basically about ideology and opposition to the kind of world that fossil fuels have been instrumental in building. CO2 and global warming are merely the hooks via which their opposition has been able to gain traction. Take away the CO2 problem via CCS, and what's left? In that sense CCS really does threaten what they care about.

Aerosol-based SRM, on the other hand, "solves" the global warming problem associated with higher CO2 levels in the atmosphere, but does nothing about ocean acidification. I see the latter as at least as great a threat to global ecosystems as rapid warming.